THE heart of Sydney smells like lots of things, but rarely the pungent odour of pepper.

During a routine bike ride through the city today, I found myself in the middle of remarkable scenes as protestors vented their rage over a controversial US film that portrays the prophet Muhammad as a womaniser and paedophile.

The protest first exploded in Martin Place, where bottles were hurled at police. One was dragged unconscious from the crowds and pepper spray was deployed.

By the time I arrived, the crowd had moved to a corner of Hyde Park, where about 200 chanted, prayed and waved signs bearing messages such as: “Our dead are in paradise, your dead are in hell.”

They were met by an overwhelming number of general duty police, as well as officers from the public order and riot squad, mounted police unit and dog squad. About a dozen ambulances were on standby.

The most striking image was of a small boy, probably no older than three, holding above his head a placard reading: “Behead all those who insult the prophet.”

The sign kept falling down but the boy’s mother continued to prop it back up so she could take pictures. Lots of pictures. Onlookers – mostly tourists and weekend shoppers - were horrified. The boy's mother was beaming.

But the calm was fractured when an onlooker screamed "Shame on you for promoting murder in the name of religion”. A contingent of protestors charged the man, punching and kicking him. Police rushed in and dragged him to safety. Other protestors urged calm.

Barely 15 minutes later, the crowd erupted again. I’m not sure what triggered it, because I was caught up in the rush and pushed down a set of stairs. When I got back up, the scene was nothing short of chaotic.

People had been arrested, onlookers and protestors had been injured (I went past one unconscious-looking young teenager who had to be carried out of the park) and the crowd had scattered east towards William Street.

In hindsight, the final melee was probably a good thing. It brought an increasingly tense standoff to a head and helped dissipate the crowd. The protest ended by about 6pm, about five hours after it all started.

As of this evening, eight people had been arrested and six police had been treated for injuries.

When I arrived home tonight, I switched on the evening news and visited some news websites. The footage failed to truly convey the crowd’s aggression, anger and deep sense of offense. It will, however, spark another round of soul-searching over religious and racial tolerance in Australia.